Step 1: In a medium-sized heavy-bottomed saucepan or Dutch oven, heat the olive oil or butter over medium heat. Once shimmering, whisk in the flour. Cook, stirring constantly, for 1-2 minutes until the mixture turns a light golden brown and smells slightly nutty, creating a roux.
Step 2: Reduce the heat to low. Add the chili powder, ground cumin, dried oregano, and garlic powder (if using) to the roux. Stir continuously for 30 seconds to 1 minute, allowing the spices to bloom and become fragrant. Be careful not to burn them.
Step 3: Gradually pour in the low-sodium broth, whisking constantly to prevent lumps. Continue whisking until the mixture is smooth. Stir in the tomato paste.
Step 4: Increase the heat to medium-low and bring the sauce to a gentle simmer, whisking occasionally. Once simmering, reduce the heat to low, cover, and let the sauce cook for 15-20 minutes, stirring every few minutes, until it thickens to your desired consistency.
Step 5: Remove the sauce from the heat. Stir in the salt, black pepper, and cayenne pepper (if using). Taste and adjust seasonings as needed. If you prefer a smoother sauce, carefully blend it using an immersion blender or transfer it to a regular blender (use caution with hot liquids).
Step 6: Your homemade enchilada sauce is now ready to use! It can be used immediately or stored for later.